In many solar energy collecting systems, water, or water with an anti-freeze liquid, comprises the heat exchange liquid. However water is far from an ideal heat exchange liquid since it has a heat absorption ratio of only about 1200 BTUs per pound. Therefore the solar collecting and utilization equipment must be fairly bulky and expensive in order to achieve effective solar energy collection.
According to the present invention, a heat exchange liquid concentrate, and a concentrate and water mixture, are provided which have numerous advantages over conventional heat, exchange liquids utilized in solar energy collection systems, and other conventional heat exchange systems. The heat exchange liquid according to the invention is a non-combustible, non-toxic, biodegradable liquid with a pH of between about 7.4-7.6, and will not harm any conventional equipment presently in use in solar energy collecting systems. Thus the heat exchange liquid according to the present invention is essentially as environmentally sound as water; yet it has enormous practical advantages compared to water. The heat absorption rate of the heat exchange liquid according to the present invention is between 100,000 BTUs per pound (when the liquid comprises about 30 percent concentrate and 80 percent water), and about one million BTUs per pound (when the liquid comprises substantially pure concentrate). Circulating in a typical closed loop solar collection system, the heat exchange liquid according to the invention can be expected to produce at least one million BTUs per day in moderate sunlight.
The novel heat exchange liquid according to the present invention allows a design of solar energy collection and utilization systems that may be much smaller than conventional systems, or can have a higher rating given the same size. The heat exchange liquid according to the invention may be substituted in place of presently existing heat exchange liquids now in use in a wide variety of heat exchange applications, particularly solar energy collecting applications, and the heat exchange liquid according to the invention may be designed for use in any environment so that it will not boil or freeze (depending upon the percentage of concentrate to water in the liquid, a freezing point as low as -100.degree. F., and a boiling temperature as high as 950.degree. F. can be obtained).
The heat exchange liquid concentrate according to the present invention includes as the major component thereof a linear alkylate sulfonate (i.e. a linear alkylbenzene sulfonate), non-ionic detergent and lauric superamide detergent mixture, such as those shown in U.S. Pat. 4,248,733 (the disclosure of which is hereby incorporated by reference herein). A superamide is a highly active fatty acid in the monoethanolamide group. The detergent mixture is mixed with a dark colored coloring agent, preferably black vegetable color comprising an amount of about 0.5-2 percent by weight of the detergent mixture. The concentrate also includes a means for increasing the heat absorption rate and the boiling temperature thereof, and preferably also for reducing the freezing temperature thereof. Such means preferably comprise vitamin B-6 in an amount of about 0.5-1 percent by weight of the detergent mixture, and either bicarbonate of soda (where lowering of the freezing point is necessary or desirable), or alfalfa (where lowering of the freezing temperature is not necessary). When utilized, the bicarbonate of soda is provided in an amount of about 3-50 percent by weight of the detergent mixture, and the alfalfa (i.e. finely ground alfalfa grains), when utilized, is in an amount of about 15-35 percent by weight of the detergent mixture.
The invention also comprises a method of effecting heat exchange between a surrounding environment and a heat exchange liquid flowing in a closed path, comprising the step of passing a heat exchange liquid comprising a non-combustible, non-toxic, biodegradable liquid having a heat absorption rate in the range between about 40,000 BTUs per pound--one million BTUs per pound in the closed path in heat exchange relationship with the surrounding environment. The heat exchange liquid is of course the preferred concentrate set forth above mixed with water, the concentrate comprising about 20-99.9 percent of the concentrate-water mixture.
The invention also comprises a method of collecting solar energy, and ultimately utilizing the energy collected, comprising the steps of: Disposing a solar energy heat collecting apparatus in a position to receive incident solar radiation thereon. Passing a heat exchange liquid in a closed loop within a heat conductive conduit system into operative heat exchange relationship with the solar energy heat collecting apparatus, the heat exchange liquid comprising a linear alkylate sulfonate, non-ionic detergent and lauric superamide detergent mixture, a dark coloring agent, and water. And at a heat sink, remote from the solar heat collecting apparatus, passing the heat exchange liquid into operative association with the heat sink so that heat collected by the heat exchange liquid is given up to the heat sink. The heat exchange liquid is of course the preferred concentrate set forth above mixed with water, the concentrate comprising about 20-99.9 percent of the concentrate-water mixture.
It is the primary object of the present invention to provide an environmentally sound, readily utilizable, high heat absorption rate heat exchange liquid, particularly adapted for use in solar energy collecting and like heat exchange systems. This and other objects of the invention will become clear an inspection of the detailed description of the invention, and from the appended claims.